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Advice to the Minister for Environment Protection, Heritage and the Arts
from the Threatened Species Scientific Committee (the Committee)
on Amendment to the list of Threatened Species
under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act)
The species is commonly known as the koala. It is the only species in the Family Phascolarctidae.
2. Reason for Conservation Assessment by the Committee
This advice follows assessment of information provided by the Committee nomination to list the koala. The Threatened Species Scientific Committee prepared the nomination and conducted the assessment at the request of the Minister.
This is the Committee’s second consideration of the species under the EPBC Act. The species was also considered under the previous Act.
3. Summary of Conclusion
The Committee judges that the species is not eligible for listing on the EPBC Act list of threatened species at this time.
The species is conventionally accepted as Phascolarctos cinereus (Goldfuss, 1817). It is commonly known as the koala.
Three subspecies of koala have been described: Phascolarctos cinereus adustus (Thomas 1923) (Queensland), P. c. cinereus (Goldfuss 1817 in (Iredale and Troughton 1934) (New South Wales) and P.c. victor (Troughton 1935) (Victoria). These are currently recognised by the Australian Biological Resources Study however their validity has been questioned by genetic and morphological anlayses (see discussion at 7.2).
The koala is a tree-dwelling, medium-sized marsupial with a stocky body, large rounded ears, sharp claws and variable but predominantly grey-coloured fur. Males generally are larger than females and there is a gradient in body weight from north to south across their range, with larger individuals in the south and smaller individuals in the north. The average weight of males is 6.5 kg in Queensland, compared with 12 kg in Victoria. Koalas in the north tend to have shorter, silver-grey fur, whereas those in the south have longer, thicker, brown-grey fur (Martin and Handasyde 1999).
6. National Context
The koala is endemic to Australia, and is widespread in coastal and inland areas from north-eastern Queensland to Eyre Peninsula in South Australia (Figure 1) . The range extends over 22o of latitude and 18o of longitude, encompassing more than one million square kilometres (Martin and Handasyde 1999). The koala’s distribution is not continuous across this range and it occurs in a number of populations that are separated by cleared land or unsuitable habitat (Martin and Handasyde 1999; NSW DECC 2008).
6.1 Natural Range
The natural range of the koala, which can be inferred from the estimated distribution of the species prior to European settlement in Australia, extends from north-eastern Queensland to the south-east corner of South Australia (ANZECC 1998). This is similar to the current range.
As a consequence of translocations, several koala populations occur outside the species’ natural range. These include the Kangaroo Island, Eyre Peninsula, Riverland and Adelaide Hills populations in South Australia. As there are no records of natural occurrences on any Victorian islands (ANZECC 1998), the koala populations on Phillip Island, French Island, Snake Island and Raymond Island in Victoria occur outside the species’ natural range (Menkhorst 2008). Similarly, there are introduced koala populations on several islands off the Queensland coast, including Brampton, St. Bees, and Magnetic Islands (Melzer et al. 2000), which could be considered outside the species’ natural range. Populations on Newry and Rabbit Islands were believed to be introduced, but recent anecdotal evidence suggests that they may be natural ( Lee submitted 2009; Ellis 2010 personal communication).
Not all populations that have wholly or partly originated from translocations occur outside the species’ natural range. There are several re-introduced populations, in the Australian Capital Territory, mainland Victoria and the south-east of South Australia, which occur within the koala’s natural range (Natural Resource Management Ministerial Council 2010).
6.2 Distribution in the States and Territories
Koala populations are scattered throughout Queensland (Queensland EPA 2006), in moist forests along the coast, subhumid woodlands in southern and central Queensland, and in some eucalypt woodlands along watercourses in the semiarid environments of the western part of the state (Melzer et al. 2000). Koalas have also been found to occur in non-riverine communities in semiarid areas (Sullivan et al. 2003a). Koalas also occur on islands off the Queensland coast: populations on St. Bees and Magnetic Islands were introduced, whereas the populations on North Stradbroke, Newry and Rabbit Islands may be natural (Melzer et al. 2000; Lee submitted 2009; Ellis 2010 personal communication).
Biogeographic regions of Queensland where koalas have been recorded include the Einasleigh Uplands, Wet Tropics, Desert Uplands, Central Mackay Coast, Mitchell Grass Downs, Mulga Lands, Brigalow Belt, South Eastern Queensland and Channel Country (Patterson 1996). In addition, koalas are present in the northern parts of several biogeographic regions that extend into New South Wales.
The greatest density of koalas in the state occurs in south-east Queensland, and lower densities occur through central, and western areas (Queensland EPA 2006). For example, population densities range from moderately high in south-east Queensland and some parts of central Queensland (e.g. 1-3 koalas per hectare) to low in other parts of central Queensland (0.01 koalas per hectare) (Melzer et al. 2000 and references therein).
6.2.2 New South Wales
In New South Wales, koalas inhabit a range of forest and woodland communities, including coastal forests, woodlands on the tablelands and western slopes, and woodland communities along watercourses in the western plains (NSW DECC 2008). Many of these areas have no current population estimates available.
Koalas mainly occur on the Central and North Coasts, although significant populations also exist on the Western Slopes and Plains, such as in the Pilliga region and Gunnedah and Walgett local government areas. Koalas are known from a number of sites on the Central and Southern Tablelands and there are also records from the Northern Tablelands. Koalas occur in sparse, and possibly disjunct, populations on the South Coast (Jurskis and Potter 1997; NSW DECC 2008; Allen et al. 2009).
Population densities range from high in parts of the NSW North Coast (e.g. 3 koalas per hectare in an artificially planted reserve at Tucki Tucki (Gall 1980)) to very low (0.006 koalas per hectare (Jurskis and Potter 1997)) near Eden on the South Coast.
6.2.3 Australian Capital Territory
In the Australian Capital Territory, it is thought that there may be currently relatively low density populations of koalas through the Tidbinbilla and Brindabella Ranges, around Bushfold, and in Orroral Valley, Namadgi National Park (Fletcher 2009 personal communication).
There have been several introductions of koalas from Victoria into the ACT between 1939 and the present. It is likely that the current koala population in the ACT is derived mainly from these deliberate introductions, although it is possible that some koalas originate from surviving local populations (Fletcher 2009 personal communication).
In Victoria, the koala population was reduced to extremely low numbers by the 1920s, but a re-introduction program over 75 years has resulted in koalas occupying most of the suitable habitat available in the state (Menkhorst 2004). Koalas are widespread in the low altitude forests and woodlands across central and southern mainland Victoria, and also occur on four islands (Raymond, Snake, French and Phillip) (Menkhorst 2004, 2008). Koalas are largely absent from the arid woodlands in the north-west and the high altitude areas of the north-east (Martin and Handasyde 1999).
In Victoria, large regional koala populations occur in the Strathbogie Ranges, Cape Otway, South Gippsland (including the Strzelecki Ranges), forests of the Naracoorte Coast Plain Bioregion, forests and woodlands on Mt Eccles lava flow (between Mt Eccles and Tyrendarra) and the Victorian Midlands Bioregion.
In Victorian forests and woodlands, the population density of koalas is generally less than one koala per hectare (Menkhorst 2004). However, there are several sites where koalas can be at greater densities, including the Strathbogie Ranges, Cape Otway, Mt Eccles National Park, Warrandyte State Park, French Island and Raymond Island (Menkhorst 2008). In some areas, the high density of koalas is putting unsustainable browsing pressure on tree species (Martin 1985a; McLean 2003). These areas include Mt Eccles National Park, Snake Island, Raymond Island and parts of the Otway Ranges (Menkhorst 2008). Some of these populations are subject to population management programs.
6.2.5 South Australia
The koala was presumed extinct in South Australia in 1924 (Wood Jones 1924), but has subsequently been introduced to five locations in the state, including Kangaroo Island, the Riverland, Eyre Peninsula, Adelaide Hills and the South East which was the only area from which they had previously been recorded (Melzer et al. 2000).
Koalas were introduced to Kangaroo Island from French Island (Victoria) in the 1920s and it now supports a large population of koalas, which is putting unsustainable browsing pressure on preferred food tree species such as manna gum (Eucalyptus viminalis) and is subject to a population-control program (Masters et al. 2004). Prior to this program, the population density in some areas exceeded 5.5 koalas per hectare (Masters et al. 2004).
Koalas were translocated from Kangaroo Island to three sites in the Riverland between 1959 and 1965. The current Riverland population is thought to be low in numbers and widely dispersed (Robinson et al. 1989). In 1969, koalas from Kangaroo Island were also translocated to Mikkira on southern Eyre Peninsula, and this population has successfully established and dispersed into adjacent areas (Melzer et al. 2000).
Koalas were introduced to the Mount Lofty Ranges in the 1930s and 1960s from Queensland, Victoria, South Australia (Kangaroo Island and possibly the South East of South Australia and possibly New South Wales. The population has since expanded throughout the Adelaide Hills region (Bryan 1996). A preliminary survey in 2003 indicated that there are areas with high population densities in the Adelaide Hills (2.4 to 8.9 koalas per hectare) (SA Govt 2005).
The koala population in South Australia’s South East was re-introduced from Kangaroo Island. Non-sterilised koalas were introduced prior to 1997 and approximately 3000 sterilised koalas have been introduced since 1997 as part of the Kangaroo Island population-control program (Masters et al. 2004; Duka and Masters 2005).
6.3 Status in Jurisdictions Across Distribution
The koala is found across several jurisdictions and has variable threatened species status as outlined below. It should be noted that the koala has been the subject of a variety of conservation plans, including the National Koala Conservation Strategy 1998 (ANZEC 1998) and National Koala Conservation and Management Strategy 2009-14 (Natural Resources Management Ministerial Council 2009). Additionally, it is the subject of a state management strategy in Victoria (DSE 2004), a recovery plan and specific state environmental planning policy in New South Wales (DECC 2008), and a Koala Response Strategy in Queensland that includes a south east Queensland koala conservation state planning policy, a net gain koala habitat offsets policy and $45.5 M for net expansion of koala habitat (DERM 2010).
7. Relevant Biology/Ecology
7.1 Life History
Female koalas can potentially produce up to one offspring each year, with births occurring between October and May but averages tend to be lower, ranging from 0.3-0.8 per year (McLean 2003). The newly-born koala lives in its mother’s pouch for 6-8 months and after leaving the pouch remains dependent on the mother, riding on its back. Young koalas are independent from 12 months of age. The generation length of koalas was estimated to be 6-8 years by Phillips (2000). Additional data from Phillips for other north eastern New South Wales sites, Pilliga and south east Queensland continues to support a figure of approximately 6 years (Phillips 2009 personal communication). Generation times from Victorian populations ranged from 4.5 years (Snake Island) to 6.0 years (Framlingham, French Island) (McLean 2010 personal communication). Population growth rates estimated for koalas range from doubling times of 3.2 in Chlamydia free, high quality habitat on French Island to 20 years (Phillips 2000; McLean 2003).
Longevity in the wild is more than 15 years for females and more than 12 years for males (Martin and Handasyde 1999). Mortality rates per annum at two sites in Queensland (Springsure and Oakey) were estimated to be: subadult females 17% and 16% for Springsure and Oakey respectively, adult females 9.2%/8.5%, subadult males 23%/23%, adult males 26%/26% (Penn et al. 2000). In Port Stephens, New South Wales, where dog attack is significant, mortality of subadult females was 39%, adult females 23%, subadult males 40%, adult males 40% (Lunney et al. 2004).
7.2 Genetic and Morphological Variation
Three subspecies of koala have been described but their validity has been questioned by genetic and morphological analyses (Takami et al. 1998; Houlden et al. 1999). The subspecies boundaries are along state boarders, but these boundaries are unlikely to represent natural barriers to koala dispersal, so populations on either side are unlikely to be isolated from one another. Southern koalas can be distinguished from northern koalas by physical features such as fur colour and size. However, the variation is considered to be predominantly clinal, changing gradually along the distribution of the koala in response to different environmental conditions (Bergmann’s rule), although some regional variation is apparent (Melzer 1995).
At the national scale Houlden et al. (1999) examined variation in mitochondrial DNA from over 200 individuals from 16 populations. Their principal conclusion was that there was a lack of support for the separation of the subspecies and tentative support for a single evolutionarily significant unit for the species. Individual populations were strongly differentiated, suggesting limited gene flow and a pattern of isolation by distance. Gene flow has been further restricted by contemporary habitat fragmentation. The appropriate management unit for koalas was suggested to be the local population (Houlden et al. 1999). The exception to the trend of population differentiation was the majority of Victorian populations (except Strzelecki Ranges and South Gippsland) and South Australian populations, which are all descendants of island populations in Victoria because of their translocation program.
Latitudinal clines may reflect important differences of adaptation to factors such as temperature, and there may also be east-west differences in adaptation. Therefore, loss of all the sub-populations in any one part of the range could reduce the ecological amplitude of the species and would certainly diminish the genetic variation (Sherwin et al. 2000).
Sherwin et al. (2000) noted that no studies had enough detail to allow mapping of the boundaries between management units. Additional studies have been undertaken since then that examine genetic variability at smaller scales. In the south east Queensland region known as the Koala Coast, a 375 km2 area in the eastern part of Brisbane, koalas have been shown by microsatellite analysis to be distinct from adjacent populations and should be considered a distinct management unit (Lee et al. 2009). This differentiation was interpreted to be recent, as a function of isolation due to barriers to dispersal imposed by roads and urban development.
Similar research has been conducted in other areas of New South Wales, but is still in the preliminary stages (Lee 2010 personal communication). In western Sydney, three populations with very limited gene flow between them have been identified (Lee et al. 2010).
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